looking for a reputable visa service

Over the years I have used several different visa services with good results. However, it does add considerably to the cost! In some cases, there’s no choice (for instance, China if you don’t live near a consulate.) But you should be able to get a tourist visa from Vietnam through their e-visa service. Be sure you’re using Vietnam’s official website, not one of the many “services” advertised online.

If you still want to use a visa service, here are two reputable ones that I have used:

https://www.pvsinternational.org/

https://abriggs.com/

What specific challenges are you having? It's all online and very easy to do yourself.

For Vietnam, you can apply online yourself for an e-visa if you're only going for 90 days or less. This is the official website: https://evisa.gov.vn/

I used a highly reputable service for my Vietnam visa last year. My friend traveling with me applied for hers online at the official website. She received her visa promptly paying just the required visa fee. I paid for the service and then had to follow-up repeatedly with the company because of their inefficiency.

Use the official site that @Cat VH mentioned above to apply for evisa.

I got my visa online as others have said. I got help and guidance, specifically on the visa process (including what to do at the airport on arrival), and generally on my 2 week visit from the tripadvisor forums.

I would think that you would only need a visa service if emigrating or travelling for work or education. Tourists should, in most cases, be able to apply easily via online services or at most through a local embassy.